Secretory carrier membrane proteins (SCAMPs) are a group of at least two 35-40 kD integral membrane proteins identified as major antigens on secretory vesicles recovered from rat salivary parotid acinar cells. These proteins play an essential role in the regulated exocytic pathway, as microinjection of a monoclonal antibody to SCAMPs perturb this process. Further characterization of SCAMP function in vivo would be greatly aided by the identification of a SCAMP homolog in a more genetically tractable system. To this end, the phylogenetic distribution of SCAMP homology will be assessed, initially in a limited number of mammalian species, then subsequently in several lower eukaryotic species with a particular emphasis towards the budding yeast, S. cerevisiae. A combination of nucleic acid hybridization and PCR-based approaches are proposed to be used in most instances, with a pair of complementary biochemical and genetic approaches to identify SCAMP homologs in yeast. We anticipate that the identification of bona fide homologs in a genetically tractable system will enable us to directly address SCAMP function in vivo, through endogenous gene replacement and directed mutagenesis.